Methods and techniques for enhancing the physical and/or mechanical properties of polyolefins are known. For example, the development of high performance ultra-high molecular weight polyethylene (UHMWPE) films and fibers has been well established, which can be achieved by using a range of unique processing techniques to avoid the generation of high entanglement density in the final products. Such techniques include film drawing and fiber spinning in the gel state. However, one drawback to some of these methods is they require a large amount of solvent. If processed by conventional melt-processing techniques with the aid of solvent, UHMWPE chains usually produce an extraordinarily high entanglement density, resulting in very low drawability or brittleness in the final product.
Carbon nanotubes, including single-wall nanotube (SWNT), multi-wall nanotube (MWNT) and carbon nanofibers (CNFs), have recently received a great deal of attention in the polymer community. Efforts have been undertaken to develop super-tough composite materials based on carbon nanotubes and polymer matrices. For example, one study has demonstrated the super-tough performance of polyvinyl alcohol (PVA)/single wall carbon nanotube (SWNT) nanocomposite fibers. Dalton et al., “Super-tough Carbon-Nanotube Fibres” Nature (2003), Vol. 423, p. 703.
These nanostructured materials have been recognized for their superior mechanical strength, excellent thermal conductivity and electrical conductivity, and thus may be utilized to improve the properties of various polymers.
Carbon nanofibers are potentially useful in reinforced composites, as supports for catalysts in high temperature reactions, heat management, reinforcement of elastomers, filters for liquids and gases, and as a component of protective clothing. Nanofibers of carbon or polymers are likely to find applications in reinforced composites, substrates for enzymes and catalysts, applying pesticides to plants, textiles with improved comfort and protection, advanced filters for aerosols or particles with nanometer scale dimensions, aerospace thermal management applications, and sensors with fast response times to changes in temperature and chemical environment.
In the case of mechanical enhancement, all published work on polymeric nanocomposites containing carbon nanotubes indicate that the improvement is only incremental; substantially below the expectation of the super-tough performance of polyvinyl alcohol (PVA)/SWNT nanocomposite fibers demonstrated by Dalton et al. described above.
Nanofibers having enhanced mechanical and electrical characteristics, including enhanced strength and fire retardant capabilities, thus remain desirable, as are composites including such nanofibers.